The present invention relates to novel polynucleotides encoding cell cycle checkpoint polypeptides.
The mitotic cell cycle is the process by which a cell creates an exact copy of its chromosomes and then segregates each copy into two cells. The sequence of events of the cell cycle is carefully regulated such that cell division does not occur until the cell has completed DNA replication and, DNA replication does not occur until cells have completed mitosis. If a cell is exposed to DNA damage, the damage is repaired before the cell undergoes cell division. Regulation of these processes ensures that an exact copy of DNA is propagated to the daughter cells. The cell cycle has been divided into four phases: G1, S, G2, and M. During the G1 phase, cells undergo activities that prepare for DNA replication. S, or synthesis, phase begins as cells initiate DNA replication and ends with the formation of two identical copies of each chromosome. G2, the stage that begins after replication is complete, is when cells ensure that they contain components needed for mitosis. M phase, or mitosis, is the stage at which the cells divide each identical chromosome into two daughter cells.
Cells have mechanisms for sensing correct cell cycle progression and exposure to DNA damage, and proteins involved in these sensing mechanisms are termed checkpoints. Checkpoints signal cell cycle arrest to allow for completion of relevant events or repair of DNA damage. There are checkpoints that monitor progression through the cycle at G1, S, G2, and M. DNA damage checkpoints also exist at these stages of the cell cycle. Failure to correct DNA damage may signal the cell to undergo programmed cell death or apoptosis.
Members of the phosphatidylinositol kinase (PIK)-related family of kinases are involved in cell cycle checkpoints and DNA damage repair. To date, five PIK-related protein kinases have been identified. Genes in this family, which includes ATM, ATR, FRAP and DNA-PKcs, encode large proteins (280-450 kD) that exhibit homology to kinases at the carboxy terminus. While the predicted amino acid sequences of the kinase domains are most closely related to lipid kinases, all have been shown to function as protein kinases, and, presumably, each of these proteins participate in a signal transduction cascade leading to cell cycle arrest, cell cycle progression, and/or DNA repair.
The ataxia-telangiectasia mutated (ATM) gene product has been shown to play a role in a DNA damage checkpoint in response to ionizing radiation (IR). Patients lacking functional ATM develop the disease ataxia-telangiectasia (A-T). Symptoms of A-T include extreme sensitivity to irradiation, cerebellar degeneration, oculocutaneous telangiectasias, gonadal deficiencies, immunodeficiencies, and increased risk of cancer [Lehman and Carr, Trends in Genet. 11:375-377 (1995)]. Fibroblasts derived from these patients show defects in G1, S, and G2 checkpoints [Painter and Young, Proc. Natl. Acad. Sci. (USA) 77:7315-7317 (1980)] and are defective in their response to irradiation. ATM is thought to sense double strand DNA damage caused by irradiation and radiomimetic drugs, and to signal cell cycle arrest so that the damage can be repaired.
The DNA-stimulated protein kinase, DNA-PKcs has been demonstrated to play an important role in repair of double strand breaks. Mice defective in DNA-PK demonstrate immunodeficiencies and sensitivity to irradiation. In addition, these mice are defective in V(D)J recombination. These results suggest that DNA-PK plays a role in repairing normal double strand DNA breaks generated during V(D)J recombination, as well as double strand breaks generated by DNA damaging agents. While DNA-PK defective cells have not been shown to be deficient in cell cycle checkpoints, it is reasonable to assume that the cell cycle must arrest, if only transiently, in order to repair double strand breaks.
ATR has been found to act as a checkpoint protein stimulated by agents that cause double strand DNA breaks, agents that cause single strand DNA breaks, and agents that block DNA replication [Cliby, et al., EMBO J. 17:159-169 (1998); Wright, et al., Proc. Natl. Acad. Sc. (USA) 95:7445-7450 (1998)]. Overexpression of ATR in muscle cells on iso-chromosome 3q results in a block to differentiation, gives rise to abnormal centrosome numbers and chromosome instability, and abolishes the G1 arrest in response to irradiation [Smith, et al. Nat. Genetics 19:39-46 (1998)]. Overexpression of a dominant negative mutant of ATR sensitizes cells to irradiation and cisplatinum [Cliby, et al., supra] and the cells fail to arrest in G2 in response to irradiation. ATR is found associated with chromosomes in meiotic cells where DNA breaks and abnormal DNA structures that persist as a result of the process of meiotic recombination [Keegan, et al, Genes Dev. 10:2423-2437 (1996)]. These data suggest that ATR, like ATM, senses DNA damage and effects a cell cycle arrest in order to allow for DNA repair.
FRAP, the target of the potent immunosuppressent rapamycin, has been demonstrated to be involved in the control of translation initiation and progression through the G1 phase of the cell cycle in response to nutrients [Kuruvilla and Shrieber, Chemisty and Biology 6:R129-R136 (1999)]. FRAP regulates translation initiation by phosphorylation of the p70S6K protein kinase and the 4E-BP1 translation regulator. While ATM, ATR, and DNA-PK are thought to sense lesions in nucleic acids, FRAP is thought to sense intracellular levels of amino acids pools. In cells lacking proper nutrients that are amino acid starved, uncharged amino acid levels rise. FRAP may sense these uncharged amino acids, become activated, and signal G1 cell cycle arrest [Kuruvilla and Shreiber, supra]
In yeast, Tor1p and Tor2p proteins show significant homology to FRAP. Both Tor1p and Tor2p are sensitive to rapamycin and both are involved in initiation of translation as well as G1 progression in response to nutrient conditions. Tor2p also plays a role in organization of actin cytoskeleton, but this activity is not blocked by rapamycin. These observations suggest that Tor2p stimulates two distinct signal transduction pathways.
An additional PIK-related family member, TRRAP, was recently identified as a member of a protein complex containing the cell cycle regulators, c-myc and E2F-1 [McMahon et al., Cell 94:363-374 (1998)]. While TRRAP shows significant sequence homology to the protein kinase domain of the other PIK-related kinases, the protein lacks critical residues required for protein kinase activity. Studies have failed to show protein kinase activity, but others have shown that TRRAP contains a histone acetyltransferase (HAT) activity. Interestingly, overexpression of TRRAP dominant inhibiting mutants or anti-sense constructs of TRRAP blocked oncogenic transformation of cultured cells transformed by c-myc or the viral oncogene, E1A [McMahon et al., supra]. These results suggest that TRRAP also plays an important role in regulating cell cycle progression and preventing oncogenesis.
In general, the proteins in this family of kinases play important roles in surveillance of DNA and cell cycle progression in order to insure genetic integrity from generation to generation. All cancer cells have a dysfunctional cell cycle and continue through the cell cycle in an inappropriate manner, either by failing to respond to negative growth signals or by failing to die in response to the appropriate signal. In addition, most cancer cells lack genomic integrity and often have an increased chromosome count compared to normal cells. Inhibitors of cell cycle checkpoints or DNA damage repair in combination with the cytotoxic agents may force cancer cells to die by forcing them to continue to progress through the cell cycle in the presence of DNA damaging agents such that they undergo catastrophic events that lead to cell death. Further, inhibitors of cell cycle progression may act to inhibit activation of cells involved in an inflammatory response and therefore inhibit inflammation.
Thus there exists a need in the art to identify additional members of the family of PIK-related kinases, and in particular, those that play roles in regulation of cell cycle progression, cell cycle checkpoints, and DNA damage repair.
The present invention provides purified and isolated Atr-2 polypeptides. In one aspect, the Atr-2 polypeptide comprises the amino acid sequence set out in SEQ ID NO: 2. The invention also provides mature Atr-2 polypeptides, preferably encoded by a polynucleotide comprising the sequence set out in SEQ ID NO: 1. Atr-2 polypeptides of the invention include those encoded by a polynucleotide selected from the group consisting of: a) the polynucleotide set out in SEQ ID NO: 1; b) a polynucleotide encoding a polypeptide encoded by the polynucleotide of (a), and c) a polynucleotide that hybridizes to the complement of the polynucleotide of (a) or (b) under moderately stringent conditions.
The invention also provides polynucleotides encoding Atr-2 polypeptides. In one aspect, the Atr-2 encoding polynucleotide comprises the sequence set forth in SEQ ID NO: 1. The invention also provides polynucleotides encoding a human Atr-2 polypeptide selected from the group consisting of: a) the polynucleotide set out in SEQ ID NO: 1; b) a polynucleotide encoding a polypeptide encoded by the polynucleotide of (a), and c) a polynucleotide that hybridizes to the complement of the polynucleotide of (a) or (b) under moderately stringent conditions. Polynucleotides of the invention include DNA molecules, cDNA molecules, genomic DNA molecules, as well as wholly or partially chemically synthesized DNA molecule. The invention further provide fragments of polynucleotides of the invention, and preferably fragments of the polynucleotide set out in SEQ ID NO: 1.
Antisense polynucleotides which specifically hybridize with the complement of a polynucleotide of the invention are also provided.
The invention further provides expression constructs comprising a polynucleotide of the invention, as well as host cells transformed or transfected with an expression construct of the invention.
Method for producing an Atr-2 polypeptide are also provided, comprising the steps of: a) growing a transformed or transfected host cell of the invention under conditions appropriate for expression of the Atr-2 polypeptide and b) isolating the Atr-2 polypeptide from the host cell or medium of the host cell""s growth.
The invention also provides antibodies specifically immunoreactive with a polypeptide of the invention. Preferably, the antibodies are monoclonal antibodies. Hybridomas which produce the antibodies are also provided, as are anti-idiotype antibodies specifically immunoreactive with an antibody of the invention.
The invention further provides methods to identify a binding partner compound of an Atr-2 polypeptide comprising the steps of: a) contacting the Atr-2 polypeptide with a compound under conditions which permit binding between the compound and the Atr-2 polypeptide; and b) detecting binding of the compound to the Atr-2 polypeptide. Preferably, the binding partner modulates activity of the Atr-2 polypeptide. In one aspect the binding partner inhibits activity of the Atr-2 polypeptide, and in another aspect, binding partner enhances activity of the Atr-2 polypeptide.
The invention also provide methods to identify a binding partner compound of an Atr-2-encoding polynucleotide of the invention steps of: a) contacting the Atr-2-encoding polynucleotide with a compound under conditions which permit binding between the compound and the Atr-2-encoding polynucleotide; and b) detecting binding of the compound to the Atr-2-encoding polynucleotide. Preferably, the specific binding partner modulates expression of an Atr-2 polypeptide encoded by the Atr-2-encoding polynucleotide. In one aspect, the binding partner compound inhibits expression of the Atr-2 polypeptide, while in another aspect, the binding partner compound enhances expression of the Atr-2 polypeptide.
The invention further provides compounds identified by methods of the invention, as well as compositions comprising a compound identified by a method of the invention and a pharmaceutically acceptable carrier.
In brief, the present invention provides purified and isolated polynucleotides encoding Atr-2 polypeptides. The invention includes both naturally occurring and non-naturally occurring Atr-2-encoding polynucleotides. Naturally occurring polynucleotides of the invention include distinct gene species within the Atr-2 family, including, for example, allelic and splice variants, as well as species homologs (or orthologs) expressed in cells of other animals. Non-naturally occurring Atr-2 encoding polynucleotides include analogs or variants of the naturally occurring products, such as insertion variants, deletion variants, substitution variants, and derivatives, as described below. In a preferred embodiment, the invention provides a polynucleotide comprising the sequence set forth in SEQ ID NO: 1. The invention also embraces polynucleotides encoding the amino acid sequence set out in SEQ ID NO: 2. A presently preferred polypeptide of the invention comprises the amino acid sequence set out in SEQ ID NO: 2. Anti-sense polynucleotides are also provided.
The invention also provides expression constructs (or vectors) comprising polynucleotides of the invention, and host cells comprising a polynucleotide or an expression construct of the invention. Methods to produce a polypeptide of the invention are also comprehended. The invention further provides antibodies, preferably monoclonal antibodies, specifically immunoreactive with a polypeptide of the invention, as well as hybridomas that secrete the antibodies.
The invention also provides Atr-2 polypeptides encoded by a polynucleotide of the invention. Atr-2 polypeptides include naturally and non-naturally occurring species. The invention further provides binding partner compounds that interact with an Atr-2 polypeptide of the invention. Methods to identify binding partner compounds are also provided, as well as methods to identify modulators of Atr-2 polypeptide biological activity.
The invention also provides materials and methods to regulate expression of Atr-2 including ribozymes, anti-sense polynucleotides, and compounds that form triplet helix.
Gene therapy techniques are also provided to modulate disease states associated with Atr-2 expression and/or biological activity.
The invention also provides compositions, and preferably pharmaceutical compositions, comprising an Atr-2 polypeptide, an Atr-2 antibody, a modulator of Atr-2 expression or biological activity, or a combination of these compounds. When compositions of the invention, and in particulary pharmaceutical compositions, are used for therapeutic or prophylactic intervention, the compounds can include one or more pharmaceutically acceptable carriers. Methods of packaging a composition of the invention, as well as methods for delivery and therapeutic treatment are also provided.
In one aspect, the invention provides novel purified and isolated human polynucleotides (e.g., DNA sequences and RNA transcripts, both sense and complementary anti-sense strands, including splice variants thereof) encoding the human Atr-2 polypeptides. DNA sequences of the invention include genomic and cDNA sequences as well as wholly or partially chemically synthesized DNA sequences. Genomic DNA of the invention comprises the protein coding region for a polypeptide of the invention and includes allelic variants of the preferred polynucleotide of the invention. Genomic DNA of the invention is distinguishable from genomic DNAs encoding polypeptides other than Atr-2 in that it includes the Atr-2 protein coding region found in Atr-2-encoding cDNA of the invention. Genomic DNA of the invention can be transcribed into RNA, and the resulting RNA transcript may undergo one or more splicing events wherein one or more introns (i.e., non-coding regions) of the transcript are removed, or xe2x80x9cspliced out.xe2x80x9d xe2x80x9cPeptide nucleic acids (PNAs)xe2x80x9d [Corey, TIBTech 15:224-229 (1997)] encoding a polypeptide of the invention are also contemplated. PNAs are DNA analogs containing neutral amide backbone linkages that are resistant to DNA degradation enzymes and which bind to complementary sequences at higher affinity than analogous DNA sequences as a result of the neutral charge on the backbone of the molecule. RNA transcripts that can be spliced by alternative mechanisms, and therefore be subject to removal of different RNA sequences but still encode an Atr-2 polypeptide, are referred to in the art as splice variants which are embraced by the invention. Splice variants comprehended by the invention therefore are encoded by the same DNA sequences but arise from distinct mRNA transcripts. Allelic variants are known in the art to be modified forms of a wild type gene sequence, the modification resulting from recombination during chromosomal segregation or exposure to conditions which give rise to genetic mutation. Allelic variants, like wild type genes, are inherently naturally occurring sequences (as opposed to non-naturally occurring variants which arise from in vitro manipulation).
The invention also comprehends cDNA that is obtained through reverse transcription of an RNA polynucleotide encoding Atr-2, followed by second strand synthesis of a complementary strand to provide a double stranded DNA. xe2x80x9cChemically synthesizedxe2x80x9d as used herein and understood in the art, refers to polynucleotides produced by purely chemical, as opposed to enzymatic, methods. xe2x80x9cWhollyxe2x80x9d chemically synthesized DNA sequences are therefore produced entirely by chemical means, and xe2x80x9cpartiallyxe2x80x9d synthesized DNAs embrace those wherein only portions of the resulting DNA were produced by chemical means.
A preferred DNA sequence encoding a human Atr-2 polypeptide is set out in SEQ ID NO: 1. The worker of skill in the art will readily appreciate that the preferred DNA of the invention comprises a double stranded molecule, for example, the molecule having the sequence set forth in SEQ ID NO: 1 along with the complementary molecule (the xe2x80x9cnon-coding standxe2x80x9d or xe2x80x9ccomplementxe2x80x9d) having a sequence deducible from the sequence of SEQ ID NO: 1 according to Watson-Crick base pairing rules for DNA. In addition, single stranded polynucleotides, including RNA as well as coding and noncoding DNAs, are also embraced the invention. Also preferred are polynucleotides encoding the Atr-2 polypeptide of SEQ ID NO: 2.
The invention further embraces species, preferably mammalian, homologs of the human Atr-2 DNA. Species homologs (also known in the art as orthologs), in general, share at least 35%, at least 40%, at least 45%, at least 50%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% homology with a human DNA of the invention. Percent sequence xe2x80x9chomologyxe2x80x9d with respect to polynucleotides of the invention is defined herein as the percentage of nucleotide bases in the candidate sequence that are identical to nucleotides in the Atr-2 sequence after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity as discussed below.
The polynucleotide sequence information provided by the invention makes possible large scale expression of the encoded Atr-2 polypeptide by techniques well known and routinely practiced in the art. Polynucleotides of the invention also permit identification and isolation of polynucleotides encoding related Atr-2 polypeptides by well known techniques including Southern and/or Northern hybridization, polymerase chain reaction (PCR), and variations of PCR. Examples of related polynucleotides include human and non-human genomic sequences, including allelic variants, as well as polynucleotides encoding polypeptides homologous to Atr-2 and structurally related polypeptides sharing one or more biological, immunological, and/or physical properties of Atr-2.
The disclosure of a full length polynucleotide encoding an Atr-2 polypeptide makes readily available to the worker of ordinary skill in the art every possible fragment of the full length polynucleotide. The invention therefore provides fragments of Atr-2-encoding polynucleotides comprising at least 10 to 20, and preferably at least 15, consecutive nucleotides of a polynucleotide encoding Atr-2, however, the invention comprehends fragments of various lengths. Preferably, fragment polynucleotides of the invention comprise sequences unique to the Atr-2-encoding polynucleotide, and therefore hybridize under highly stringent or moderately stringent conditions only (i.e., xe2x80x9cspecificallyxe2x80x9d or xe2x80x9cexclusivelyxe2x80x9d) to polynucleotides encoding Atr-2, or Atr-2 fragments thereof, containing the unique sequence. Polynucleotide fragments of genomic sequences of the invention comprise not only sequences unique to the coding region, but also include fragments of the full length sequence derived from introns, regulatory regions, and/or other non-translated sequences. Sequences unique to polynucleotides of the invention are recognizable through sequence comparison to other known polynucleotides, and can be identified through use of alignment programs routinely utilized in the art, e.g., those made available in public sequence databases.
The invention also provides fragment polynucleotides that are conserved in one or more polynucleotides encoding members of the Atr-2 family of polypeptides. Such fragments include sequences characteristic of the family of Atr-2 polynucleotides, and are also referred to as xe2x80x9csignature sequences.xe2x80x9d The conserved signature sequences are readily discernable following simple sequence comparison of polynucleotides encoding members of the Atr-2 family. Fragments of the invention can be labeled in a manner that permits their detection, including radioactive and non-radioactive labeling.
Fragment polynucleotides are particularly useful as probes for detection of full length or other fragment Atr-2 polynucleotides. One or more fragment polynucleotides can be included in kits that are used to detect the presence of a polynucleotide encoding Atr-2, or used to detect variations in a polynucleotide sequence encoding Atr-2, including polymorphisms, and particularly single nucleotide polymorphisms. Kits of the invention optionally include a container and/or a label.
The invention also embraces naturally or non-naturally occurring Atr-2-encoding polynucleotides that are fused, or ligated, to a heterologous polynucleotide to encode a fusion (or chimeric) protein comprising all or part of an Atr-2 polypeptide. xe2x80x9cHeterologousxe2x80x9d polynucleotides include sequences that are not found adjacent, or as part of, Atr-2-encoding sequences in nature. The heterologous polynucleotide sequence can be separated from the Atr-2-coding sequence by an encoded cleavage site that will permit removal of non-Atr-2 polypeptide sequences from the expressed fusion protein. Heterologous polynucleotide sequences can include those encoding epitopes, such as poly-histidine sequences, FLAG(copyright) tags, glutathione-S-transferase, thioredoxin, and/or maltose binding protein domains, that facilitate purification of the fusion protein; those encoding domains, such as leucine zipper motifs, that promote multimer formation between the fusion protein and itself or other proteins; and those encoding immunoglobulins or fragments thereof that can enhance circulatory half-life of the encoded protein.
The invention also embraces DNA sequences encoding Atr-2 species that hybridize under highly or moderately stringent conditions to the non-coding strand, or complement, of the polynucleotide in SEQ ID NO: 1. Atr-2-encoding polynucleotides of the invention include a) the polynucleotide set out in SEQ ID NO: 2; b) polynucleotides encoding a polypeptide encoded by the polynucleotide of (a), and c) polynucleotides that hybridize to the complement of the polynucleotides of (a) or (b) under moderately or highly stringent conditions. Exemplary high stringency conditions include a final wash in 0.2xc3x97SSC/0.1% SDS at 65xc2x0 C. to 75xc2x0 C., and exemplary moderate stringency conditions include a final wash at 2xc3x97 to 3xc3x97SSC/0.1% SDS at 65xc2x0 C. to 75xc2x0 C. It is understood in the art that conditions of equivalent stringency can be achieved through variation of temperature and buffer, or salt concentration as described in Ausubel, et al. (Eds.), Protocols in Molecular Biology, John Wiley and Sons (1994), pp. 6.0.3 to 6.4.10. Modifications in hybridization conditions can be empirically determined or precisely calculated based on the length and the percentage of guanosine/cytosine (GC) base pairing of the probe. The hybridization conditions can be calculated as described in Sambrook, et al., (Eds.), Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press: Cold Spring Harbor, N.Y. (1989), pp. 9.47 to 9.51.
Autonomously replicating recombinant expression constructs such as plasmid and viral DNA vectors incorporating Atr-2-encoding sequences are also provided. Expression constructs wherein Atr-2-encoding polynucleotides are operatively linked to an endogenous or exogenous expression control DNA sequence and a transcription terminator are also provided. Expression control DNA sequences include promoters, enhancers, and/or operators, and are generally selected based on the expression systems in which the expression construct is to be utilized. Preferred promoter and enhancer sequences are generally selected for the ability to increase gene expression, while operator sequences are generally selected for the ability to regulate gene expression. It is understood in the art that the choice of host cell is relevant to selection of an appropriate regulatory sequence. Expression constructs of the invention may also include sequences encoding one or more selectable markers that permit identification of host cells bearing the construct. Expression constructs may also include sequences that facilitate, and preferably promote, homologous recombination in a host cell. Preferred constructs of the invention also include sequences necessary for replication in a host cell.
Expression constructs are preferably utilized for production of an encoded protein, but may also be utilized to amplify the construct itself when other amplification techniques are impractical.
According to another aspect of the invention, host cells are provided, including prokaryotic and eukaryotic cells, comprising a polynucleotide of the invention in a manner which permits expression of the encoded Atr-2 polypeptide. Polynucleotides of the invention may be introduced into the host cell as part of a circular plasmid, or as linear DNA comprising an isolated protein coding region or a viral vector. Methods for introducing DNA into the host cell well known and routinely practiced in the art include transformation, transfection, electroporation, nuclear injection, or fusion with carriers such as liposomes, micelles, ghost cells, protoplasts, and other transformed cells. Expression systems of the invention include bacterial, yeast, fungal, plant, insect, invertebrate, and mammalian cells systems.
Host cells of the invention are a valuable source of immunogen for development of antibodies specifically, i.e., exclusively, immunoreactive with Atr-2. Host cells of the invention are also useful in methods for large scale production of Atr-2 polypeptides wherein the cells are grown in a suitable culture medium and the desired polypeptide products are isolated from the cells or from the medium in which the cells are grown by purification methods known in the art, e.g., conventional chromatographic methods including immunoaffinity chromatography, receptor affinity chromatography, hydrophobic interaction chromatography, lectin affinity chromatography, size exclusion filtration, cation or anion exchange chromatography, high pressure liquid chromatography (HPLC), reverse phase HPLC, and the like. Still other methods of purification include those wherein the desired protein is expressed and purified as a fusion protein having a specific tag, label, or chelating moiety that is recognized by a specific binding partner or agent. The purified protein can be cleaved to yield the desired protein, or be left as an intact fusion protein. Cleavage of the fusion component may produce a form of the desired protein having additional amino acid residues as a result of the cleavage process.
Knowledge of Atr-2-encoding DNA sequences allows for modification of cells to permit, or increase, expression of endogenous Atr-2. Cells can be modified (e.g., by homologous recombination) to provide increased Atr-2 expression by replacing, in whole or in part, the naturally occurring Atr-2 promoter with all or part of a heterologous promoter so that the cells express Atr-2 at higher levels. The heterologous promoter is inserted in such a manner that it is operatively linked to Atr-2-encoding sequences. See, for example, PCT International Publication No. WO 94/12650, PCT International Publication No. WO 92/20808, and PCT International Publication No. WO 91/09955. It is also contemplated that, in addition to heterologous promoter DNA, amplifiable marker DNA (e.g., ada, dhfr, and the multifunctional CAD gene which encodes carbamyl phosphate synthase, aspartate transcarbamylase, and dihydroorotase) and/or intron DNA may be inserted along with the heterologous promoter DNA. If linked to the Atr-2 coding sequence, amplification of the marker DNA by standard selection methods results in co-amplification of the Atr-2 coding sequences in the cells.
The DNA sequence information provided by the present invention also makes possible the development through, e.g. homologous recombination or xe2x80x9cknock-outxe2x80x9d strategies [Capecchi, Science 244:1288-1292 (1989)], of animals that fail to express functional Atr-2 or that express a variant of Atr-2. Such animals are useful as models for studying the in vivo activities of Atr-2 and modulators of Atr-2.
The invention also provides purified and isolated mammalian Atr-2 polypeptides encoded by a polynucleotide of the invention. Presently preferred is a human Atr-2 polypeptide comprising the amino acid sequence set out in SEQ ID NO: 2. Mature Atr-2 polypeptides are also provided, wherein leader and/or signal sequences are removed. The invention also embraces Atr-2 polypeptides encoded by a DNA selected from the group consisting of: a) the polynucleotide set out in SEQ ID NO: 1; b) polynucleotides encoding a polypeptide encoded by the polynucleotide of (a), and c) polynucleotides that hybridize to the complement of the polynucleotides of (a) or (b) under moderate or high stringency conditions.
The invention also embraces polypeptides have at least 99%,at least 95%, at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, at least 55% or at least 50% identity and/or homology to the preferred polypeptide of the invention. Percent amino acid sequence xe2x80x9cidentityxe2x80x9d with respect to the preferred polypeptide of the invention is defined herein as the percentage of amino acid residues in the candidate sequence that are identical with the residues in the Atr-2 sequence after aligning both sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Percent sequence xe2x80x9chomologyxe2x80x9d with respect to the preferred polypeptide of the invention is defined herein as the percentage of amino acid residues in the candidate sequence that are identical with the residues in the Atr-2 sequence after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and also considering any conservative substitutions as part of the sequence identity.
In one aspect, percent homology is calculated as the percentage of amino acid residues in the smaller of two sequences which align with identical amino acid residue in the sequence being compared, when four gaps in a length of 100 amino acids are introduced to maximize alignment [Dayhoff, in Atlas of Protein Sequence and Structure, Vol. 5, p. 124, National Biochemical Research Foundation, Washington, D.C. (1972), incorporated herein by reference].
Preferred methods to determine identity and/or similarity are designed to give the largest match between the sequences tested. Methods to determine identity and similarity are codified in publicly available computer programs. Preferred computer program methods to determine identity and similarity between two sequences include, but are not limited to, the GCG program package, including GAP (Devereux, J., et al., Nucleic Acids Research 12(1):387 (1984); Genetics Computer Group, University of Wisconsin, Madison, Wis.), BLASTP, BLASTN, and FASTA (Atschul, S. F. et al., J. Molec. Biol. 215:403-410 (1990). The BLAST X program is publicly available from the National Center for Biotechnology Information (NCBI) and other sources (BLAST Manual, Altschul, S., et al. NCB NLM NIH Bethesda, Md. 20894; Altschul, S., et al., J. Mol. Biol. 215:403-410 (1990). The well known Smith Waterman algorithm may also be used to determine identity.
By way of example, using the computer algorithm GAP (Genetics Computer Group, University of Wisconsin, Madison, Wis.), two polypeptides for which the percent sequence identity is to be determined are aligned for optimal matching of their respective amino acids (the xe2x80x9cmatched spanxe2x80x9d, as determined by the algorithm). A gap opening penalty (which is calculated as 3xc3x97 the average diagonal; the xe2x80x9caverage diagonalxe2x80x9d is the average of the diagonal of the comparison matrix being used; the xe2x80x9cdiagonalxe2x80x9d is the score or number assigned to each perfect amino acid match by the particular comparison matrix) and a gap extension penalty (which is usually 1/10 times the gap opening penalty), as well as a comparison matrix such as PAM 250 or BLOSUM 62 are used in conjunction with the algorithm. A standard comparison matrix (see Dayhoff et al., in: Atlas of Protein Sequence and Structure, vol. 5, supp.3 [1978] for the PAM250 comparison matrix; see Henikoff et al., Proc. Natl. Acad. Sci USA, 89:10915-10919 [1992] for the BLOSUM 62 comparison matrix) is also used by the algorithm.
Preferred parameters for polypeptide sequence comparison include the following:
Algorithm: Needleman and Wunsch, J. Mol. Biol. 48:443-453 (1970),
Comparison matrix: BLOSUM 62 from Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 89:10915-10919 (1992).
Gap Penalty: 12
Gap Length Penalty: 4
Threshold of Similarity: 0
The GAP program is useful with the above parameters. The aforementioned parameters are the default parameters for polypeptide comparisons (along with no penalty for end gaps) using the GAP algorithm.
Preferred parameters for nucleic acid molecule sequence comparison include the following:
Algorithm: Needleman and Wunsch, J. Mol Biol. 48:443-453 (1970)
Comparison matrix: matches=+10, mismatch=0
Gap Penalty: 50
Gap Length Penalty: 3
The GAP program is also useful with the above parameters. The aforementioned parameters are the default parameters for nucleic acid molecule comparisons.
Other exemplary algorithms, gap opening penalties, gap extension penalties, comparison matrices, thresholds of similarity, etc. may be used by those of skill in the art, including those set forth in the Program Manual, Wisconsin Package, Version 9, September, 1997. The particular choices to be made will depend on the specific comparison to be made, such as DNA to DNA, protein to protein, protein to DNA; and additionally, whether the comparison is between pairs of sequences (in which case GAP or BestFit are generally preferred) or between one sequence and a large database of sequences (in which case FASTA or BLASTA are preferred).
Certain alignment schemes for aligning two amino acid sequences may result in matching of only a short region of the two sequences, and this small aligned region may have very high sequence identity even though there is no significant relationship between the two full length sequences. Accordingly, in a preferred embodiment, the selected alignment method will result in an alignment that spans at least about 66 contiguous amino acids of the claimed full length polypeptide.
Polypeptides of the invention may be isolated from natural cell sources or may be chemically synthesized, but are preferably produced by recombinant procedures involving host cells of the invention. Use of mammalian host cells is expected to provide for such post-translational modifications. (e.g., glycosylation, truncation, lipidation, and phosphorylation) as may be needed to confer optimal biological activity on recombinant expression products of the invention. Glycosylated and non-glycosylated form of Atr-2 polypeptides are embraced.
The invention also embraces variant (or analog) Atr-2 polypeptides.
In one example, insertion variants are provided wherein one or more amino acid residues supplement an Atr-2 amino acid sequence. Insertions may be located at either or both termini of the protein, or may be positioned within internal regions of the Atr-2 amino acid sequence. Insertional variants with additional residues at either or both termini can include for example, fusion proteins and proteins including amino acid tags or labels. Insertion variants include Atr-2 polypeptides wherein one or more amino acid residues are added to a fragment of an Atr-2 amino acid sequence. Variant products of the invention also include mature Atr-2 products, i.e., Atr-2 polypeptide products wherein leader or signal sequences are removed, and additional amino terminal residues have been inserted. The additional amino terminal residues may be derived from another protein, or may include one or more residues that are not identifiable as being derived from a specific protein. Atr-2 products with an additional methionine residue at position xe2x88x921 (Metxe2x88x921-Atr-2) are contemplated, as are Atr-2 products with additional methionine and lysine residues at positions xe2x88x922 and xe2x88x921 (Metxe2x88x922-Lysxe2x88x921-Atr-2). Variants of Atr-2 with additional Met, Met-Lys, Lys residues (or one or more basic residues in general) are particularly useful for enhanced recombinant protein production in bacterial host cell. Heterologous amino acid sequences can also include protein transduction domains that target the lipid bilayer of a cell membrane and permit protein transduction into cells in an indiscriminate manner [Schwarze, et al., Science 285.:1569-1572 (1999)]. Fusion polypeptides of this type are particularly well suited for delivery to the cytoplasm and nucleus of cells, and also to cells across the blood-barrier.
The invention also embraces Atr-2 variants having additional amino acid residues which result from use of specific expression systems. For example, use of commercially available vectors that express a desired polypeptide as part of glutathione-S-transferase (GST) fusion product provides the desired polypeptide having an additional glycine residue at position xe2x88x921 after cleavage of the GST component from the desired polypeptide. Variants which result from expression in other vector systems are also contemplated.
Insertional variants also include fusion proteins wherein the amino and/or carboxy termini of the Atr-2-polypeptide is fused to another polypeptide. Examples of other polypeptides are immunogenic polypeptides, proteins with long circulating half life such as immunoglobulin constant regions, marker proteins (e.g., fluorescent, chemiluminescence, enzymes, and the like) proteins or polypeptide that facilitate purification of the desired Atr-2 polypeptide, and polypeptide sequences that promote formation of multimeric proteins (such as leucine zipper motifs that are useful in dimer formation/stability). Fusion proteins wherein an Atr-2 polypeptide is conjugated to a hapten or other agent to improve, i.e., enhance, immungenicity, are also provided.
In another aspect, the invention provides deletion variants wherein one or more amino acid residues in an Atr-2 polypeptide are removed. Deletions can be effected at one or both termini of the Atr-2 polypeptide, or with removal of one or more residues within the Atr-2 amino acid sequence. Deletion variants, therefore, include all fragments of an Atr-2 polypeptide. Disclosure of the complete Atr-2 amino acid sequences necessarily makes available to the worker of ordinary skill in the art every possible fragment of the Atr-2 polypeptide.
The invention also embraces polypeptide fragments of the sequence set out in SEQ ID NO: 2 wherein the fragments maintain biological, immunological, physical, and/or chemical properties of an Atr-2 polypeptide. Fragments comprising at least 5, 10, 15, 20, 25, 30, 35, or 40 consecutive amino acids of SEQ ID NO: 2 are comprehended by the invention. Preferred polypeptide fragments display antigenic and/or biological properties unique to or specific for the Atr-2 family of polypeptides. Fragments of the invention having the desired biological and immunological properties can be prepared by any of the methods well known and routinely practiced in the art.
In still another aspect, the invention provides substitution variants of Atr-2 polypeptides. Particularly preferred variants include dominant negative mutants that lack kinase activity. Substitution variants include those polypeptides wherein one or more amino acid residues of an Atr-2 polypeptide are removed and replaced with alternative residues. In one aspect, the substitutions are conservative in nature, however, the invention embraces substitutions that are also non-conservative. Conservative substitutions for this purpose may be defined as set out in Tables A, B, or C below.
Variant polypeptides include those wherein conservative substitutions have been introduced by modification of polynucleotides encoding polypeptides of the invention. Amino acids can be classified according to physical properties and contribution to secondary and tertiary protein structure. A conservative substitution is recognized in the art as a substitution of one amino acid for another amino acid that has similar properties. Exemplary conservative substitutions are set out in Table A (from WO 97/09433, page 10, published Mar. 13, 1997 (PCT/GB96/02197, filed Sep. 6, 1996), immediately below, wherein amino acids are listed by standard one letter designations.
Alternatively, conservative amino acids can be grouped as described in Lehninger, [Biochemistry, Second Edition; Worth Publishers, Inc. NY:NY (1975), pp.71-77] as set out in Table B, immediately below.
As still an another alternative, exemplary conservative substitutions are set out in Table C, immediately below.
The invention also provides derivatives of Atr-2 polypeptides. Derivatives include Atr-2 polypeptides bearing modifications other than insertion, deletion, or substitution of amino acid residues. Preferably, the modifications are covalent in nature, and include for example, chemical bonding with polymers, lipids, other organic, and inorganic moieties. Derivatives of the invention may be prepared to increase circulating half-life of a Atr-2 polypeptide, to improve targeting capacity for the polypeptide to desired cells, tissues, or organs, and/or to modulate (increase or decrease) biological and/or immunological activity.
The invention further embraces Atr-2 products covalently modified or derivatized to include one or more water soluble polymer attachments such as polyethylene glycol, polyoxyethylene glycol, polypropylene glycol or any of the many other polymers well known in the art, including, for example, monomethoxy-polyethylene glycol, dextran, cellulose, or other carbohydrate based polymers, poly-(N-vinyl pyrrolidone)-polyethylene glycol, propylene glycol homopolymers, a polypropylene oxide/ethylene oxide co-polymer, polyoxyethylated polyols (e.g., glycerol) and polyvinyl alcohol, as well as mixtures of these polymers. Particularly preferred are Atr-2 products covalently modified with polyethylene glycol (PEG) subunits. Water soluble polymers may be bonded at specific positions, for example at the amino terminus of the Atr-2 products, or randomly attached to one or more side chains of one or more amino acid residues in the polypeptide.
The invention further comprehends Atr-2 polypeptides having combinations of insertions, deletions, substitutions, or derivatizations.
Also comprehended by the present invention are antibodies (e.g., monoclonal and polyclonal antibodies, single chain antibodies, chimeric antibodies, bifunctional/bispecific antibodies, humanized antibodies, human antibodies, bispecific antibodies, and complementary determining region (CDR)-grafted antibodies/proteins, including compounds which include CDR and/or antigen-binding sequences, which specifically recognize a polypeptide of the invention) and other binding proteins specific for Atr-2 products or fragments thereof. Preferred antibodies of the invention are human antibodies which are produced and identified according to methods described in WO93/11236, published Jun. 20, 1993, which is incorporated herein by reference in its entirety. Antibody fragments, including Fab, Fabxe2x80x2, F(abxe2x80x2)2, and Fv, are also provided by the invention. The term xe2x80x9cspecific forxe2x80x9d indicates that the variable regions of the antibodies of the invention recognize and bind Atr-2 polypeptides exclusively (i.e., able to distinguish Atr-2 polypeptides from the family of ATR polypeptides despite sequence identity, homology, or similarity found in the family of polypeptides), but may also interact with other proteins (for example, S. aureus protein A or other antibodies in ELISA techniques) through interactions with sequences outside the variable or CDR regions of the antibodies, and in particular, in the constant region of the molecule. Screening assays to determine binding specificity or exclusivity of an antibody of the invention are well known and routinely practiced in the art. For a comprehensive discussion of such assays, see Harlow et al. (Eds), Antibodies A Laboratory Manual; Cold Spring Harbor Laboratory; Cold Spring Harbor, N.Y. (1988), Chapter 6. Antibodies that recognize and bind fragments of the Atr-2 polypeptides of the invention are also contemplated, provided that the antibodies are first and foremost specific or exclusive for, as defined above, Atr-2 polypeptides. As with antibodies that are specific for full length Atr-2 polypeptides, antibodies of the invention that recognize Atr-2 fragments are those which can distinguish Atr-2 polypeptides from the family of ATR polypeptides despite inherent sequence identity, homology, or similarity found in the family of proteins.
Antibodies of the invention can be produced using any method well known and routinely practiced in the art, using any polypeptide, or immunogenic fragment thereof, of the invention. Immunogenic polypeptides can be isolated from natural sources, from recombinant host cells, or can be chemically synthesized. Protein of the invention may also be conjugated to a hapten such as keyhole limpet hemocyanin (KLH) in order to increase immunogenicity. Methods for synthesizing such peptides are known in the art, for example, as in R. P. Merrifield, J. Amer. Chem. Soc. 85: 2149-2154 (1963); J. L. Krstenansky, et al., FEBS Lett. 211:10 (1987). Antibodies to a polypeptide of the invention can also be prepared through immunization using a polynucleotide of the invention, as described in Fan et al., Nat. Biotech. 17:870-872 (1999). DNA encoding a polypeptide may be used to generate antibodies against the encoded polypetide following topical administration of naked plasmid DNA or following injection, and preferably intramuscular injection, or the DNA.
Non-human antibodies may be humanized by any methods known in the art. In one method, the non-human CDRs are inserted into a human antibody or consensus antibody framework sequence. Further changes can then be introduced into the antibody framework to modulate affinity or immunogenicity.
Antibodies of the invention further include plastic antibodies or molecularly imprinted polymers (MIPs) [Haupt and Mosbauch, TIBTech 16:468-475) (1998)]. Antibodies of this type are particularly useful in immunoaffinity separation, chromatography, soli phase extraction, immunoassays, for use as immunosensors, and for screening chemical or biological libraries. A typical method of preparation is described in Haupt and Mosbauch [supra]. Advatanges of antibodies of this type are that no animal immunization is required, the antibodies are relatively inexpensive to produce, they are resistant to organic solvents, and they are reusable over long period of time.
Antibodies of the invention can also include one or more labels that permit detection of the antibody, and in particular, antibody binding. Labels can include, for example, radioactivity, fluorescence (or chemiluminescence), one of a high affinity binding pair (e.g. ,biotin/avidin), enzymes, or combinations of one or more of these labels.
Antibodies of the invention are useful for, for example, therapeutic purposes (by modulating activity of Atr-2), diagnostic purposes to detect or quantitate Atr-2, as well as purification of Atr-2. Kits comprising an antibody of the invention for any of the purposes described herein are also comprehended. In general, a kit of the invention also includes a control antigen for which the antibody is immunospecific. Kits of the invention optionally include a container and/or a label.
The DNA and amino acid sequence information provided by the present invention also makes possible the systematic analysis of the structure and function of Atr-2. DNA and amino acid sequence information for Atr-2 also permits identification of binding partner compounds with which an Atr-2 polypeptide or polynucleotide will interact. Methods to identify binding partner compounds include solution assays, in vitro assays wherein Atr-2 polypeptides are immobilized, and cell based assays. Identification of binding partner compounds of Atr-2 polypeptides provides potential targets for therapeutic or prophylactic intervention in pathologies associated with Atr-2 biological activity.
Specific binding proteins can be identified or developed using isolated or recombinant Atr-2 products, Atr-2 variants or analogs, or cells expressing such products. Binding proteins are useful for purifying Atr-2 products and detection or quantification of Atr-2 products in fluid and tissue samples using known immunological procedures. Binding proteins are also manifestly useful in modulating (i.e., blocking, inhibiting, or stimulating) biological activities of Atr-2, especially those activities involved in signal transduction or biological pathways in general wherein Atr-2 participates directly or indirectly.
In solution assays, methods of the invention comprise the steps of (a) contacting an Atr-2 polypeptide with one or more candidate binding partner compounds and (b) identifying the compounds that bind to the Atr-2 polypeptide. Identification of the compounds that bind the Atr-2 polypeptide can be achieved by isolating the Atr-2 polypeptide/binding partner complex, and separating the Atr-2 polypeptide from the binding partner compound. An additional step of characterizing the physical, biological, and/or biochemical properties of the binding partner compound is also comprehended in another embodiment of the invention. In one aspect, the Atr-2 polypeptide/binding partner complex is isolated using a antibody immunospecific for either the Atr-2 polypeptide or the candidate binding partner compound. In another aspect, the complex is isolated using a second binding partner compound that interacts with either the Atr-2 polypeptide or the candidate binding partner compound.
In still another embodiment, either the polypeptide Atr-2 or the candidate binding partner compound comprises a label or tag that facilitates its isolation, and methods of the invention to identify binding partner compounds include a step of isolating the Atr-2 polypeptide/binding partner complex through interaction with the label or tag. An exemplary tag of this type is a poly-histidine sequence, generally around six histidine residues, that permits isolation of a compound so labeled using nickel chelation. Other labels and tags, such as the FLAG(copyright) tag (Eastman Kodak, Rochester, N.Y.), thioredoxin, and/or maltose binding protein, each of which is well known and routinely used in the art and are embraced by the invention.
In an in vitro assay, methods of the invention comprise the steps of (a) contacting an immobilized Atr-2 polypeptide with a candidate binding partner compound and (b) detecting binding of the candidate compound to the Atr-2 polypeptide. In an alternative embodiment, the candidate binding partner compound is immobilized and binding of the Atr-2 polypeptide is detected. Immobilization is accomplished using any of the methods well known in the art, including covalent bonding to a support, a bead, or a chromatographic resin, as well as non-covalent, high affinity interaction such as antibody binding, or use of streptavidin/biotin binding wherein the immobilized compound includes a biotin or streptavidin moiety. Detection of binding can be accomplished (i) using a radioactive label on the compound that is not immobilized, (ii) using of a fluorescent label on the non-immobilized compound, (iii) using an antibody immunospecific for the non-immobilized compound, (iv) using a label on the non-immobilized compound that excites a fluorescent support to which the immobilized compound is attached, as well as other techniques well known and routinely practiced in the art.
In cell based assays of the invention to identify binding partner compounds of an Atr-2 polypeptide, methods comprise the steps of contacting an Atr-2 polypeptide in a cell with a candidate binding partner compound and detecting binding of the candidate binding partner compound to the Atr-2 polypeptide. A presently preferred method uses the dihybrid assay as previously described [Fields and Song, Nature 340:245-246 (1989); Fields, Methods: A Companion to Methods in Enzymology 5:116-124 (1993); U.S. Pat. No. 5,283,173 issued Feb. 1, 1994 to Fields, et al.]. Modifications and variations on the di-hybrid assay (also referred to in the art as xe2x80x9ctwo-hybridxe2x80x9d assay) have previously been described [Colas and Brent, TIBTECH 16:355-363 (1998)] and are embraced by the invention.
Agents that modulate (i.e., increase, decrease, or block) Atr-2 activity or expression may be identified by incubating a putative modulator with an Atr-2 polypeptide or polynucleotide and determining the effect of the putative modulator on Atr-2 activity or expression. The selectivity, or specificity, of a compound that modulates the activity of Atr-2 can be evaluated by comparing its effects on Atr-2 or an Atr-2-encoding polynucleotide to its effect on other compounds. Cell based methods, such as di-hybrid assays to identify DNAs encoding binding compounds and split hybrid assays to identify inhibitors of Atr-2 polypeptide interaction with a known binding polypeptide, as well as in vitro methods, including assays wherein an Atr-2 polypeptide, Atr-2-encoding polynucleotide, or a binding partner are immobilized, and solution assays are contemplated by the invention.
Selective modulators may include, for example, antibodies and other proteins or peptides which specifically bind to an Atr-2 polypeptide or an Atr-2-encoding nucleic acid, oligonucleotides which bind to an Atr-2 polypeptide or an Atr-2 gene sequence, and other non-peptide compounds (e.g., isolated or synthetic organic and inorganic molecules) which specifically react with an Atr-2 polypeptide or underlying nucleic acid. Preferably, modulators of the invention will bind specifically or exclusively to an Atr-2 polypeptide or Atr-2-encoding polynucleotide, however, modulators that bind an Atr-2 polypeptide or an Atr-2-encoding polynucleotide with higher affinity or avidity compared to other compounds are also contemplated. Mutant Atr-2 polypeptides which affect the enzymatic activity or cellular localization of the wild-type Atr-2 polypeptides are also contemplated by the invention. Presently preferred targets for the development of selective modulators include, for example: (1) regions of an Atr-2 polypeptide which contact other proteins, (2) regions that localize an Atr-2 polypeptide within a cell, (3) regions of an Atr-2 polypeptide which bind substrate, (4) allosteric regulatory binding site(s) of an Atr-2 polypeptide, (5) phosphorylation site(s) of an Atr-2 polypeptide as well as other regions of the protein wherein covalent modification regulates biological activity and (6) regions of an Atr-2 polypeptide which are involved in multimerization of subunits. Still other selective modulators include those that recognize specific Atr-2-encoding and regulatory polynucleotide sequences. Modulators of Atr-2 activity may be therapeutically useful in treatment of diseases and physiological conditions in which Atr-2 activity is known or suspected to be involved.
Methods of the invention to identify modulators include variations on any of the methods described above to identify binding partner compounds, the variations including techniques wherein a binding partner compound has been identified and the binding assay is carried out in the presence and absence of a candidate modulator. A modulator is identified in those instances where the level of binding between an Atr-2 polypeptide and a binding partner compound changes in the presence of the candidate modulator compared to the level of binding in the absence of the candidate modulator compound. A modulator that increases binding between an Atr-2 polypeptide and the binding partner compound is described as an enhancer or activator, and a modulator that decreases binding between the Atr-2 polypeptide and the binding partner compound is described as an inhibitor. In vitro methods of the invention are particularly amenable to high throughput assays as described below.
In addition to the assays described above which can be modified to identify binding partner compounds, other methods are contemplated which as designed to more specifically identify modulators. In one aspect, methods of the invention comprehend use of the split hybrid assay as generally described in WO98/13502, published Apr. 2, 1998. The invention also embraces variations on this method as described in WO95/20652, published Aug. 3, 1995.
The invention also comprehends high throughput screening (HTS) assays to identify compounds that interact with or inhibit biological activity (i.e., inhibit enzymatic activity, binding activity, etc.) of an Atr-2 polypeptide. HTS assays permit screening of large numbers of compounds in an efficient manner. Cell-based HTS systems are contemplated, including melanophore assays to investigate receptor-ligand interaction, yeast-based assay systems, and mammalian cell expression systems [Jayawickreme and Kost, Curr. Opin. Biotechnol. 8:629-634 (1997)]. Automated (robotic) and miniaturized HTS assays are also embraced [Houston and Banks, Curr. Opin. Biotechnol. 8:734-740 (1997)]. HTS assays are designed to identify xe2x80x9chitsxe2x80x9d or xe2x80x9clead compoundsxe2x80x9d having the desired property, from which modifications can be designed to improve the desired property. Chemical modification of the xe2x80x9chitxe2x80x9d or xe2x80x9clead compoundxe2x80x9d is often based on an identifiable structure/activity relationship (SAR) between the xe2x80x9chitxe2x80x9d and the Atr-2 polypeptide.
There are a number of different libraries used for the identification of small molecule modulators, including, (1) chemical libraries, (2) natural product libraries, and (3) combinatorial libraries comprised of random peptides, oligonucleotides or organic molecules.
Chemical libraries consist of structural analogs of known compounds or compounds that are identified as xe2x80x9chitsxe2x80x9d or xe2x80x9cleadsxe2x80x9d via natural product screening. Natural product libraries are collections from microorganisms, animals, plants, or marine organisms which are used to create mixtures for screening by: (1) fermentation and extraction of broths from soil, plant or marine microorganisms or (2) extraction of plants or marine organisms. Natural product libraries include polyketides, non-ribosomal peptides, and variants (non-naturally occurring) variants thereof. For a review, see Science 282:63-68 (1998). Combinatorial libraries are composed of large numbers of peptides, oligonucleotides or organic compounds as a mixture. They are relatively easy to prepare by traditional automated synthesis methods, PCR, cloning or proprietary synthetic methods. Of particular interest are peptide and oligonucleotide combinatorial libraries. Still other libraries of interest include peptide, protein, peptidomimetic, multiparallel synthetic collection, recombinatorial, and polypeptide libraries. For a review of combinatorial chemistry and libraries created therefrom, see Myers, Curr. Opin. Biotechnol. 8:701-707 (1997).
Identification of modulators through use of the various libraries described herein permits modification of the candidate xe2x80x9chitxe2x80x9d (or xe2x80x9cleadxe2x80x9d) to optimize the capacity of the xe2x80x9chitxe2x80x9d to modulate activity.
Also made available by the invention are anti-sense polynucleotides which recognize and hybridize to polynucleotides encoding Atr-2. Full length and fragment anti-sense polynucleotides are provided. The worker of ordinary skill will appreciate that fragment anti-sense molecules of the invention include (i) those which specifically or exclusively recognize and hybridize to Atr-2-encoding RNA (as determined by sequence comparison of DNA encoding Atr-2 to DNA encoding other molecules) as well as (ii) those which recognize and hybridize to RNA encoding variants of the Atr-2 family of proteins. Antisense polynucleotides that hybridize to RNA encoding other members of the ATR family of proteins are also identifiable through sequence comparison to identify characteristic, or signature, sequences for the family of molecules. Identification of sequences unique to Atr-2-encoding polynucleotides, as well as sequences common to the family of ATR-encoding polynucleotides, can be easily deduced through use of any publicly available sequence database, or through use of commercially available sequence comparison programs. After identification of the desired sequences, isolation through restriction digestion or amplification using any of the various polymerase chain reaction techniques well known in the art can be performed. Anti-sense polynucleotides are particularly relevant for regulating expression of Atr-2 by those cells expressing Atr-2 mRNA. Antisense molecules are generally from about 5 to about 100 nucleotide in length, and preferably are about 10 to 20 nucleotides in length. Antisense nucleic acids capable of specifically binding to Atr-2 expression control sequences or Atr-2 RNA are introduced into cells, e.g., by a viral vector or colloidal dispersion system such as a liposome.
The anti-sense nucleic acid binds to the Atr-2-encoding target nucleotide sequence in the cell and prevents transcription or translation of the target sequence. Phosphorothioate and methylphosphonate anti-sense oligonucleotides are specifically contemplated for therapeutic use by the invention. The anti-sense oligonucleotides may be further modified by poly-L-lysine, transferrin polylysine, or cholesterol moieties at their 5xe2x80x2 end.
The invention further contemplates methods to modulate Atr-2 expression through use of ribozymes. For a review, see Gibson and Shillitoe, Mol. Biotech. 7:125-137 (1997). Ribozyme technology can be utilized to inhibit translation of Atr-2 mRNA in a sequence specific manner through (i) the hybridization of a complementary RNA to a target mRNA and (ii) cleavage of the hybridized mRNA through nuclease activity inherent to the complementary strand. Ribozymes can identified by empirical methods but more preferably are specifically designed based on accessible sites on the target mRNA [Bramlage, et al., Trends in Biotech 16:434-438 (1998)]. Delivery of ribozymes to target cells can be accomplished using either exogenous or endogenous delivery techniques well known and routinely practiced in the art. Exogenous delivery methods can include use of targeting liposomes or direct local injection. Endogenous methods include use of viral vectors and non-viral plasmids.
Ribozymes can specifically modulate expression of Atr-2 when designed to be complementary to regions unique to a polynucleotide encoding Atr-2. xe2x80x9cSpecifically modulatexe2x80x9d is intended to mean that ribozymes of the invention recognize only (i.e., exclusively) a polynucleotide encoding Atr-2. Similarly, ribozymes can be designed to modulate expression of all or some of the AIR family of proteins. Ribozymes of this type are designed to recognize polynucleotide sequences conserved in all or some of the polynucleotides which encode the family of Atr-2 proteins. Preferred ribozymes bind to an Atr-2-encoding polynucleotide with a higher degree of specificity that to other polynucleotides.
The invention further embraces methods to modulate transcription of Atr-2 through use of oligonucleotide-directed triple helix formation. For a review, see Lavrovsky, et al., Biochem. Mol. Med. 62:11-22 (1997). Triple helix formation is accomplished using sequence specific oligonucleotides which hybridize to double stranded DNA in the major groove as defined in the Watson-Crick model. Hybridization of a sequence specific oligonucleotide can thereafter modulate activity of DNA-binding proteins, including, for example, transcription factors and polymerases. Preferred target sequences for hybridization include promoter and enhancer regions to permit transcriptional regulation of Atr-2 expression. In addition to use of oligonucleotides, triple helix formation techniques of the invention also embrace use of peptide nucleic acids as described in Corey, TIBTECH 15:224-229 (1997). Oligonucleotides which are capable of triple helix formation are also useful for site-specific covalent modification of target DNA sequences. Oligonucleotides useful for covalent modification are coupled to various DNA damaging agents as described in Lavrovsky, et al. [supra].
Mutations in the Atr-2 gene can result in loss of normal function of the Atr-2 gene product and underlie Atr-2-related human disease states. The invention therefore comprehends gene therapy to restore Atr-2 activity in treating those disease states described herein. Delivery of a functional Atr-2 gene to appropriate cells is effected ex vivo, in situ, or in vivo by use of vectors, and more particularly viral vectors (e.g., adenovirus, adeno-associated virus, or a retrovirus), or ex vivo by use of physical DNA transfer methods (e.g., liposomes or chemical treatments). See, for example, Anderson, Nature, supplement to vol. 392, no. 6679, pp.25-20 (1998). For additional reviews of gene therapy technology, see Friedmann, Science, 244: 1275-1281 (1989); Verma, Scientific American: 68-84 (1990); and Miller, Nature, 357: 455-460 (1992). Alternatively, it is contemplated that in some human disease states, preventing the expression of, or inhibiting the activity of, Atr-2 will be useful in treating the disease states. It is contemplated that anti-sense therapy or gene therapy (for example, wherein a dominant negative Atr-2 mutatnt is introduced into a target cell type) could be applied to negatively regulate the expression of Atr-2.
The invention also provide compositions comprising modulators of Atr-2 biological activity. Preferably, the compositions are pharmaceutical compositions. The pharmaceutical compositions optionally may include pharmaceutically acceptable (i. e., sterile and non-toxic) liquid, semisolid, or solid diluents that serve as pharmaceutical vehicles, excipients, or media. Any diluent known in the art may be used. Exemplary diluents include, but are not limited to, polyoxyethylene sorbitan monolaurate, magnesium stearate, methyl- and propylhydroxybenzoate, talc, alginates, starches, lactose, sucrose, dextrose, sorbitol, mannitol, gum acacia, calcium phosphate, mineral oil, cocoa butter, and oil of theobroma.
The pharmaceutical compositions can be packaged in forms convenient for delivery. The compositions can be enclosed within a capsule, sachet, cachet, gelatin, paper, or other container. These delivery forms are preferred when compatible with entry of the immunogenic composition into the recipient organism and, particularly, when the immunogenic composition is being delivered in unit dose form. The dosage units can be packaged, e.g., in tablets, capsules, suppositories or cachets.
The pharmaceutical compositions may be introduced into the subject to be treated by any conventional method including, e.g., by intravenous, intradermal, intramuscular, intramammary, intraperitoneal, intrathecal, intraocular, retrobulbar, intrapulmonary (e.g., aerosolized drug solutions) or subcutaneous injection (including depot administration for long term release); by oral, sublingual, nasal, anal, vaginal, or transdermal delivery; or by surgical implantation, e.g., embedded under the splenic capsule, brain, or in the cornea. The treatment may consist of a single dose or a plurality of doses over a period of time.
Compositions are generally administered in doses ranging from 1 xcexcg/kg to 100 mg/kg per day, preferably at doses ranging from 0.1 mg/kg to 50 mg/kg per day, and more preferably at doses ranging from 1 to 20 mg/kg/day. The composition may be administered by an initial bolus followed by a continuous infusion to maintain therapeutic circulating levels of drug product. Those of ordinary skill in the art will readily optimize effective dosages and administration regimens as determined by good medical practice and the clinical condition of the individual patient. The frequency of dosing will depend on the pharmacokinetic parameters of the agents and the route of administration. The optimal pharmaceutical formulation will be determined by one skilled in the art depending upon the route of administration and desired dosage. See for example, Remington""s Pharmaceutical Sciences, 18th Ed. (1990, Mack Publishing Co., Easton, Pa. 18042) pages 1435-1712, the disclosure of which is hereby incorporated by reference. Such formulations may influence the physical state, stability, rate of in vivo release, and rate of in vivo clearance of the administered agents. Depending on the route of administration, a suitable dose may be calculated according to body weight, body surface area or organ size. Further refinement of the calculations necessary to determine the appropriate dosage for treatment involving each of the above mentioned formulations is routinely made by those of ordinary skill in the art without undue experimentation, especially in light of the dosage information and assays disclosed herein, as well as the pharmacokinetic data observed in the human clinical trials discussed above. Appropriate dosages may be ascertained through use of established assays for determining blood levels dosages in conjunction with appropriate dose-response data. The final dosage regimen will be determined by the attending physician, considering various factors which modify the action of drugs, e.g. the drug""s specific activity, the severity of the damage and the responsiveness of the patient, the age, condition, body weight, sex and diet of the patient, the severity of any infection, time of administration and other clinical factors. As studies are conducted, further information will emerge regarding the appropriate dosage levels and duration of treatment for various diseases and conditions.
It will be appreciated that the pharmaceutical compositions and treatment methods of the invention may be useful in the fields of human medicine and veterinary medicine. Thus, the subject to be treated may be a mammal, preferably human, or other animals. For veterinary purposes, subjects include, for example, farm animals including cows, sheep, pigs, horses, and goats, companion animals such as dogs and cats; exotic and/or zoo animals; laboratory animals including mice, rats, rabbits, guinea pigs, and hamsters; and poultry such as chickens, turkeys, ducks and geese.
Association of Atr-2 with cell cycle progression makes compositions of the invention, including for example an Atr-2 polypeptide, an inhibitor thereof, an antibody, or other modulator of Atr-2 expression or biological activity, useful for treating any of a number of conditions. For example, aberrant Atr-2 activity can be associated with various forms of cancer in, for example, adult and pediatric oncology, including growth of solid tumors/malignancies, myxiod and round cell carcinoma, locally advanced tumors, metastatic cancer, human soft tissue sarcomas, cancer metastases, including lymphatic metastases, squamous cell carcinoma of the head and neck, esophageal squamous cell carcinoma, oral carcinoma, blood cell malignancies, including multiple myeloma, leukemias, effusion lymphomas (body cavity based lymphomas), thymic lymphoma lung cancer, including small cell carcinoma, non-small cell cancers, breast cancer, including small cell carcinoma and ductal carcinoma, gastrointestinal cancers, including stomach cancer, colon cancer, colorectal cancer, polyps associated with colorectal neoplasia, pancreatic cancer, liver cancer, urological cancers, including bladder cancer, including primary superficial bladder tumors, invasive transitional cell carcinoma of the bladder, and muscle-invasive bladder cancer, prostate cancer, malignancies of the female genital tract, including ovarian carcinoma, primary peritoneal epithelial neoplasms, cervical carcinoma, uterine endometrial cancers, and solid tumors in the ovarian follicle, kidney cancer, including renal cell carcinoma, brain cancer, including intrinsic brain tumors, neuroblastoma, astrocytic brain tumors, gliomas, metastatic tumor cell invasion in the central nervous system, bone cancers, including osteomas, skin cancers, including malignant melanoma, tumor progression of human skin keratinocytes, and squamous cell cancer, hemangiopericytoma, and Kaposi""s sarcoma. Still other conditions include aberrant apoptotic mechanisms, including abnormal caspase activity; aberrant enzyme activity associated with cell cycle progression, include for example cyclins A, B, D and E; alterations in viral (e.g., Epstein-Barr virus, papillomavirus) replication in latently infected cells; chromosome structure abnormalities, including genomic stability in general, unrepaired chromosome damage, telomere erosion (and telomerase activity), breakage syndromes including for example, Sjogren""s syndrome and Nijimegen breakage syndrome; embryonic stem cell lethality; abnormal embyonic development; sensitivity to ionizing radiation; acute immune complex alveolitis; and Fanconi anemia.